Method of anticipating machine failure

Abstract

A method of anticipating defects in the operation of a machine, especially a rotary machine in which high-frequency and low-frequency ranges of a body-wave spectrum in a solid part of the machine are detected and respective auto-spectral density functions G 11 and G 22 are formed, the cross spectral density function G 12 being formed from the measurements as well. The magnitude γ 2 =G 12 2 /G 11 ·G 22 is formed and the defect is anticipated by an increase in the value of γ 2 .

I claim: 
     
       1. In a method of operating a machine producing body waves in a machine part and in which a measurement is made of a first body-wave parameter at a relatively high-frequency range of a frequency spectrum of said body waves and a second body-wave parameter is measured in a low-frequency range of said frequency spectrum, the improvement which comprises: generating an auto-spectral density value G 11  corresponding to the measurement of said first parameter;   generating a second auto-spectral density value G 22  from said measurement of said second body-wave parameter;   generating a cross spectral density value G 12  from both of the measurements;   automatically forming the coherence function γ 2  =G 12   2  /G 11  ·G 22  ; and   detecting an increase in the value of γ 2  as an anticipation of impending failure of said machine.   
     
     
       2. The improvement defined in claim 1, further comprising the step of cutting off operating of said machine upon a rise in the value of γ 2 . 
     
     
       3. The improvement defined in claim 1, further comprising the step of generating a product γ 2  ·G 22  and detecting an increase in the value of said product as representing anticipatory failure of said machine. 
     
     
       4. The improvement defined in claim 1, further comprising the step of terminating operation of said machine upon an increase in said product. 
     
     
       5. In a system for monitoring a machine generating body waves in operation for anticipation of failure of said machine, wherein a first body-wave parameter is measured on said machine in a relatively high-frequency range of a frequency spectrum of said body waves and a second body-wave parameter is measured on said machine at a relatively low frequency of said frequency spectrum, the improvement which comprises: means for deriving respective high-frequency and low-frequency values from said measurements;   a frequency analyzing computer connected to said means for generating from said values an auto-spectral density function G 11  from said high-frequency value, a second auto-spectral density function G 22  from said low-frequency value, and a cross spectral density function G 12  from both values; and   a function generator connected to said computer for generating the function γ 2  =G 12   2  /G 11  ·G 22 , where an increase in the value of γ 2  anticipates a defect in said machine.   
     
     
       6. The system defined in claim 5, further comprising means responsive to an increase in a value of γ 2  for automatically cutting off operation of said machine. 
     
     
       7. The system defined in claim 5 wherein the means for generating said high-frequency value includes a demodulator.